The present invention relates to polyethersulfoneformals and a method for making.
Prior to the present invention, aromatic polyformals were made by forming a diphenylate preform and reacting it in the presence of an alkylene halide, such as methylene halide, in an organic solvent, as shown by Barclay, U.S. Pat. No. 3,069,386. The resulting polyformal could thereafter be phosgenated to produce an aromatic polyformal convertible to fibers and films. The resulting formal oligomer prior to phosgenation was a random block polyformal which required additional polymerization to produce a higher molecular weight material capable of being fabricated as previously indicated. In addition, the polyformal carbonates made in accordance with Barclay are hydrolytically unstable materials because of the carbonate linkages and have a relatively low glass transition temperature, for example, between 80 to 160. Improved results were achieved by effecting reaction between the alkylene halide and the dihydric phenol under insitu conditions in the presence of a phase transfer catalyst as shown by copending application of Allan S. Hay previously cited. The aromatic polyformals made in accordance with the aforementioned Hay method were formed having substantially higher intrinsic viscosities resulting in significantly improved physical properties, such as Gardner Impact values, as compared to the Aromatic polyformals of Barclay.
The present invention is based on the discovery that aromatic polyformals can be made having polyethersulfone oligomer units by initially forming a polyethersulfone oligomer having terminal phenoxide linkages as defined hereinafter, which can be reacted with an alkylene halide in the presence of an organic solvent, such as dipolar aprotic solvent. It also has been found that a nonpolar solvent can be employed in instances where a phase transfer catalyst is utilized in accordance with a procedure originally discovered by Hay in Ser. No. 958,040.